6 DISCOVERY REPORTS 



are soft and irregularly corrugated. In this region the dorsal glandular caeca [d.ca.) open into the 

 dorso-lateral angles of the lumen. Slightly posterior to these openings the dorsal ridge [d.r.) becomes 

 free from the dorsal wall and projects a short distance as a soft pad {d.p.). Similarly swellings of the 

 lateral and ventral walls split off together from the gut walls and form a trilobed chitin-covered 

 process {l.p. and rn.p.), each of whose lobes bears a long projection {p.) converging dorsally as shown 



in Fig. 3 B. 



The lateral lobes bear strong setae and are undoubtedly homologous with the lateral finger-like 

 processes of Nebalia, but the homologies of the median ventral lobe are uncertain. Thiele suggests 

 that it may be the sum of the two lateral ridges {l.r.) of Nebalia. If this were the case it might be 

 expected that some trace of the double nature would remain, but none could be found. It is more 

 likely that it is homologous with the ventral cardio-pyloric valve, the shifting of which posteriorly is 

 a slight change comparable with the other differences between the two species. A third alternative 

 is that the small pyloric pad of Nebalia (p.p. Fig. i) has been greatly enlarged, but this, like Thiele's 

 suggestion, is a major alteration involving the disappearance of the cardio-pyloric valve. 



dr. d.r' 



oesn 



m. 



Fig. 3. A. Anterior region of the fore-gut of Nebaliella looking forwards into a piece cut at region A of Fig. 2 to show the 

 relationships of the parts hidden by the median structures, a.m.p. anterior median projection; d.ch. dorsal channel ; d.r. dorsal 

 ridge; d.r.' small ridge on dorsal ridge ;^.s.i strong setae; 0.5.2 short stiff spines; m. mandible ; ow. oesophagus; o«.r. oesophageal 

 ridges. B. Posterior region of the fore-gut and the entrance to the intestine of Nebaliella looking backwards from region B 

 of Fig. 2 to show the spatial relations of the pads and the projections thereon in the pyloric part of the gut. d.gl. digestive 

 glands; /. intestine; l.p. lateral pad; m.p. median pad; p. long projections; v.p.ch. ventral pyloric chamber. 



II. MID- AND HIND-GUT 



Besides the dorsal glandular caeca already mentioned, Nebaliella resembles Nebalia in having three 

 digestive gland caeca {d.gl.) on either side. These unite and open into the ventro-lateral corners of 

 the ventral pyloric chamber {v.p.ch.) immediately posterior to the tripartite process. The openings 

 are smaller than those in Nebalia. Ventral glandular caeca were not found. 



The lumen of the intestine is relatively wider than in Nebalia, and for a considerable distance is 

 roughly triangular, with one angle dorsal and two ventro-lateral, and with walls of highly vacuolated 

 cells. Passing posteriorly the cells become less vacuolated and a striated border appears on them. 

 Then the outline of the gut becomes oval and the striated border deeper. Finally the cross-section 



